Fuel pump



F. KNECHT FUEL PUMP I May 15, 1934.

Filed Feb. 23*. 1932 z n h M 7 0m A,

' carrying out this method.

Patented May 15, 1934 PATENT FUEL PUMP Franz Knecht, Gaggenau, Germany, assignor to Daimler-Benz Aktiengesellschaft,

Stuttgart- Unterturkheim, Germany, a company of Germany Application February 23, 1932, Serial No. 594,692

. In Germany February 28, 1931 Claims.

This invention has for its object to simplify and improve the operation and regulation of fuel pumps, more particularly for Diesel engines, and consists substantially in this that the fuel is drawn in by suction during a portion only of the suction stroke of the pump, while the remaining portion of the suction stroke works idly, for instance producing a vacuum, and the sucked-in fuel is fed also only during a portion of the delivery stroke to the engine, while the remaining portion of the delivery stroke works idly, for instance doing away with the produced vacuum. By varying the moment at which the eifective part of the suction stroke is ended and the idle part of the stroke begins the quantity of fuel deliver-ed by the pump can be very simply varied.

The invention also relates to fuel As compared with the known arrangements in which the quantity of fuel is regulated by flowing over or flowing back, the invention has the advantage that only the quantity of fuel actually required for the injection is sucked and conveyed by the pump, whereby the detrimental backward and forward surging of the column of fuel, which is drawn by suction and forced back again, is avoided. At the same time an effective sealing between the suction space and the delivery space can be obtained, by replacing the edge control usually employed for regulating the flowing over or flowing back, which owing to the great pressure differences soon leads to the sliding surface of the piston becoming leaky, by a simple bore containing a non-return valve, so that the sealing at the edges can be avoided without any special complications, such as controlled valves or thelike.

In the accompanying drawing a constructional example of the invention is illustrated diagrammatically,

Fig. 1 being a section through the pump, and

Fig. 2 showing the controlling slots of the suc-.

tion pipes on two of the pump cylinders.

The pump piston b moves to and fro in the pump cylinder a and is actuated by .a cam c and a tappet c. The stroke is for instance H, the suction pipe communicates with the suction space d, the suction space communicating through the controlling slot e with the cylinder space. The controlling slot isswept past by the transverse bore 9 in the piston, which is connected by a longitudinal bore h with the pump space 2.

The latter is shut oil by the valve from the said bore and by the valve 1 from the delivery pipe 111.. The piston b can be turned in a known manner by means of a rack n and a pinion 0 about its axis pumps for so that the. bore g is displaced relatively to the control slot e. In the position shown in'the draw ing the piston is in the upper dead centre position, the bore 9 being in the position shown for instance on the left by a full line (Fig. 2). On fill the piston travelling downwards, fuel will in the first place be drawn by suction with the valve It open until the bore 9 is out oil by the controlling edge of the slot e. During the continued stroke till the bottom dead centre position 9' is reached (35 a vacuum is produced in the pump space i. During the upward stroke of the piston the vacuum thus produced is first removed again through the idle running of the piston which is followed by an efiective delivery stroke, corresponding to the 7 length of the eifective suction stroke, with the valve 7c closed and the valve Z open. The quantity of fuel sucked in is therefore always equal to the quantity actually delivered.

By turning the piston the position of the bore 9' with respect to the control slot can be changed, for instance intothe position 9 so that the total stroke H from 91 to or becomes effective. The control edge of the slot e may be a straight line or any curve. In the case of multi-cylinder engines the arrangement may forinstance be such that byv displacing the control bar (not shown), when the engine is under a light load, only some of the pump cylinders (as on the left of Fig. 2) are effective, while the others which are con- 86 trolled by a slot e work idlyand the pump cylinders only become fully effective successively either slowly or rapidly.

Furthermore the arrangement makes it possible for the part of the piston between the pump 90 space i and the suction space d along which the piston is guided in a fiuid-tight manner to be made very long, which increases the reliability of its operation. The pump might of course be constructed in another way, for instance the control edge and the bore g might be interchanged in such a manner that the former is placed in the piston and the latter in the cylinder. Instead of the piston the cylinder or a separate sliding member might be turned or some other method of regulation might be provided.

The regulation of the moment of injection can be effected in a known manner for'instance by displacing the pump cam or the like.

What I claim is: 106

1. A fuel-injecting pump for Dieselengines, comprising a cylinder having an inlet opening and an outlet opening, a reciprocating piston movably arranged in said cylinder so as to be capable of performing a suction stroke and a U0 delivery stroke and .so as to form a working chamber, said piston having a passage therein communicating with said working chamber, a. valve for obstructing the communication between 5 said working chamber and passage arranged to open only during the suction stroke so as to prevent communication between the working chamber and said passage during any portion of the delivery stroke, said piston having also-an opening therein communicating with said passage and arranged to register with said inlet opening only during the first portion of the suction stroke and the last portion of the delivery stroke and a delivery valve for closing the outlet opening, said delivery valve being capable of opening only on the pressure in the working chamber exceeding a predetermined amount.

'2. A fuel-injecting pump for Diesel engines, comprising a cylinder having an inlet opening and an outlet opening, a reciprocating piston arranged in said cylinder so as to be movable away from said outletopening to perform a V suction stroke and towards said outlet opening to perform a delivery stroke and so as to form a working chamber, said piston having a passage therein communicating with said working space, a valve for obstructing the communication between said working chamber and passage arranged to open only during the suction stroke, so as to prevent communication between the working chamber and said passage during any portion of the delivery stroke, said piston having also an opening therein communicating with said passage and arranged to register with said inlet opening only during the first portion of the suetion stroke and the last portion of the delivery stroke, means for Varying. the proportion .of the suction stroke during which the opening in the piston and the opening in the cylinder remain in registration and a delivery valve for closing the outlet opening, said delivery valve being capable of opening only on the pressure in the working chamber exceeding a predetermined amount.

3. A fuel injecting pump for Diesel engines, comprising a cylinder having an inlet opening and an outlet opening, a reciprocating piston movably arranged in said cylinder so as to be capable of performing a suction strokeahd a open during the last portion of the delivery stroke correspondingv to the said first portion of the suction stroke. c

4. A fuel injecting pump for Diesel engines, comprising a cylinder having an inlet opening and an outlet opening, a reciprocating piston moveating opening remain in registration.

ably arranged in said cylinder 50 as to be capable of performing a suction stroke and at delivery stroke and so as to form a working chamber, said piston having a passage therein communicating with said working chamber and having a'communicating opening'therein communicating with said passage'and arranged to register with said inlet opening only during the first portion. of the suction stroke and the last portion of the 4 delivery stroke, one of said openings, viz., com--v municating opening and inlet opening, having a depth which increases peripherally of the cylinder or piston respectively from a minimum to a maximum, a valve member for obstructing the communication between said working chamber and passage arranged to open only during the suction stroke so as to prevent communication between the working chamber and inletopening during any portion of the delivery stroke, a delivery valve for closing the outlet opening, said delivery valve being capable ofopening only on the pressure in": the working chamber exceeding a predetermined amount and means for producing relative rotation between the piston and the cylinder for varying the proportion of the suction stroke during which the said inlet opening and communicating opening remain in registration. 5. A fuel injecting pump for Diesel engines, comprising a cylinder having an inlet opening and an. outlet opening, a reciprocating piston movably arranged in said cylinder so as to be capable of performing a suction stroke and adelivery stroke and so as to form a working chamber, said pistonhavlng a passage therein communicating with said working chamber and having a communicating opening therein communicating with said passage and arranged to register with said inlet opening only during the flrstportion of the suction stroke and the last portion .of the delivery stroke, oneof said openings, viz., communicating opening and inlet open- -ing, having a depth which increases peripherally of the cylinder or piston respectively from a minimum to a,maximum, the rate of increase varying in different parts of the opening, a valve member for obstructing the communication between said working chamber and passage arranged to open only during the suction stroke so as to prevent communication between the working-chamber and inlet opening during any portion of the delivery stroke, a delivery valve for closing the outlet opening, said delivery valve being capable of opening only on the pressure in the, workingchamber exceeding a predetermined amount and means for producing relative rotation between the pistonand the cylinder for varying the proportion of the suction stroke during which the said inlet opening and communi- FRANZ KNECHT. 

